Lung cancer is one of the most common cancers in the world, and non-small-cell lung cancer (NSCLC) is by far the most common form, accounting for nearly 80% of those cases (Qreenlee R T., et al., CA Cancer J Clin. 2001; 51:15-36). Many genetic alterations associated with the development and progression of lung cancer have been reported. However, to date, the precise molecular mechanisms remain unclear (Sozzi G., Eur J Cancer. 2001; 37 Suppl 7:S63-73). Over the last decade newly developed cytotoxic agents, including paclitaxel, docetaxel, gemcitabine, and vinorelbine, have emerged to offer multiple therapeutic choices for patients with advanced NSCLC; however, those regimens provide only modest survival benefits compared with cisplatin-based therapies (Schiller J H, et al, N Engl J Med. 2002; 346:92-8; Kelly K, et al., J Clin Oncol. 2001; 19:3210-8). Hence, new therapeutic strategies are eagerly anticipated.
Systematic analysis of expression levels of thousands of genes using cDNA microarrays is an effective approach for identifying unknown molecules involved in pathways of carcinogenesis, and can reveal candidate target molecules for the development of novel therapeutics and diagnostics. The present inventors analyzed genome-wide expression profiles of NSCLC cells on a cDNA microarray containing 23,040 genes, using tumor-cell populations purified by laser microdissection, in an attempt to isolate potential molecular targets for diagnosis, treatment, and/or prevention of NSCLC (Kikuchi T, et al., Oncogene. 2003; 22:2192-205; Suzuki C, et al., Cancer Res. 2003; 63:7038-41; Kakiuchi S, et al., Mol Cancer Res. 2003; 1:485-99; Zembutsu H, et al., Int J Oncol. 2003; 23:29-39; Kakiuchi S, et al., Hum Mol Genet. 2004; 13:3029-43). To verify the biological and clinicopathological significance of the respective gene products, the present inventors have also performed tumor-tissue microarray analysis of clinical lung-cancer materials (Ishikawa N, et al., Clin Cancer Res. 2004; 10(24):8363-70). This systematic approach revealed that a cell division associated 1 (CDCA1) and a kinetocore associated 2 (KNTC2) were frequently co-over-expressed in primary NSCLCs (see also WO2004/031413).
Altered regulation of the cell cycle is a hallmark of human cancers. CDCA1 and KNTC2 are members of several proteins involved in spindle checkpoint signaling. Specifically, attachment sites within the kinetochore outer plate generate microtubule dependent forces for chromosome movement and regulate spindle checkpoint protein assembly at the kinetochore. The Ndc80 complex, composed of Ndc80 (Hec1), Nuf2, Spc24, and Spc25, is essential for metaphase chromosome alignment and anaphase chromosome segregation. The Ndc80 complex was first isolated in budding yeast and its homologues have been identified in worm, frog, chicken, and human (Ciferri, C. et al. J Biol Chem. 280, 29088-95 (2005).; McCleland, M. L et al. Genes Dev. 17, 101-114 (2003).; Desai, A. et al. Genes Dev. 17, 2421-2435 (2003).; DeLuca, J. G. et al. Curr Biol. 13, 2103-2109 (2003).). The attachment sites of the CDCA1-KNTC2 complex within the kinetochore outer plate generate microtubule dependent forces for chromosomal movement and regulate spindle checkpoint protein assembly at the kinetochore. Yeast cells that lost members of the complex or had mutated members were known to exhibit loss of kinetocore-microtubule attachment without global loss of kinetochore structure (Wigge, P. A. et al. J Cell Biol. 152, 349-60 (2001).). Yeast Nuf2 also disappears from the centromere during meiotic prophase, when centromeres lose their connection to the spindle pole body, and plays a regulatory role in the segregation of chromosomes (Nabetani, A. et al. Chromosoma. 110, 322-334 (2001).). Human CDCA1 was identified as a member of genes that were co-expressed with known cell cycle genes, including CDC2, cyclin, topoisomerase II and others21, and was reported to be associated with centromeres of mitotic HeLa cells; this confers the prospect that CDCA1 is a functional homolog of yeast Nuf2 (Wigge, P. A. et al. J Cell Biol. 152, 349-360 (2001).).
On the other hand, human KNTC2 was identified as an interacting protein with the C-terminus of the retinoblastoma protein (RB1) using a yeast 2-hybrid screening and was suggested to be one of several proteins involved in spindle checkpoint signaling (Durfee, T. et al. Genes Dev. 7, 555-569 (1993).; Chen, Y. et al. Mol. Cell. Biol. 17, 6049-6056 (1997).). This surveillance mechanism involving KNTC2 recruits the MPS1 kinase and MAD1/MAD2 complexes to kinetochores and assures correct segregation of chromosomes during cell division by detecting unaligned chromosomes and causing prometaphase arrest until the proper bipolar attachment of chromosomes is achieved (Martin-Lluesma, S. et al. Science 297, 2267-2270 (2002)).
Despite these advances, to date, there has been no report describing the significance of the co-activation of the CDCA1-KNTC2 complex in human cancer progression and its potential as therapeutic and prognostic targets.